New fridge freezer making hissing sound

[marb]

Just put a new Indiset fridge freezer in the kitchen and upon turning it on there seems to be some noise coming from the rear like a kind of air hissing. The fridge and freezer seem to be working fine but this Noise wasn't familiar with my old Electrolux. I also noticed when unwrapping it that there was a small black plastic rubber plug/bung that could have come out of something. Didn't see anywhere it could have come from though

Is this just settling in noise as its new ?

 

[rocks1]

It's the gas going round nothing to worry about.

 

[marb]

Ok, thanks. It's settled a lot now.